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Orientation and Structure of Ionic Liquid Cation at Air/[bmim][BF4] Aqueous Solution Interface 被引量:1
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作者 gang-hua deng Xia Li +3 位作者 You-qi Guo Shi-lin Liu Zhou Lu Yuan Guo 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2013年第5期569-575,I0004,共8页
The watermiscible room temperature ionic liquid 1butyl3methylimidazolium tetrafluorob orate ([bmim] [BF4]) is a model system for studying the interactions between ionic liquid and water molecules. In this work the o... The watermiscible room temperature ionic liquid 1butyl3methylimidazolium tetrafluorob orate ([bmim] [BF4]) is a model system for studying the interactions between ionic liquid and water molecules. In this work the orientational structure of the low concentrated aqueous solution of [bmim] [BF4] at the air/liquid interface was investigated by sum frequency gener ation vibrational spectroscopy. It has been found that at very low concentrations, the butyl chain exhibited a significant gauche defect, indicating a disordered conformation; and the cation ring oriented with a fairly small tilting angle at the surface. When the concentration increased, the cation ring tended to lie flat at the surface, and the gauche defects of the butyl chain decreased due to the intermolecular chainchain interactions and the consequent more ordered interfacial molecular arrangement. Additionally, the antisymmetric stretching mode in the PPP and SPS spectra exhibited a peak shift, showing that there exists more than one kind of orientation or chemical environment for the butyl CH3 group. These results may shed new light on understanding the surface behavior of watermiscible ionic liquids as well as the imidazolium based surfactants. 展开更多
关键词 Sum frequency generation vibratinal spectroscopy Ionic liquid Aqueous solu-tion INTERFACE ORIENTATION
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Salt effect on molecular orientation at air/liquid methanol interface 被引量:1
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作者 Xia Li gang-hua deng +5 位作者 Rong-Juan Feng Ke Lin Zhen Zhang Yu Ba Zhou Lu Yuan Guo 《Chinese Chemical Letters》 SCIE CAS CSCD 2016年第4期535-539,共5页
The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy(SFG-VS). We clarified that the average til... The salt effects on molecular orientation at air/liquid methanol interface were investigated by the polarization-dependent sum frequency generation vibrational spectroscopy(SFG-VS). We clarified that the average tilting angle of the methyl group to be u = 308 58 at the air/pure methanol surface assuming a d-function orientational distribution. Upon the addition of 3 mol/L Na I, the methyl group tilts further away from the surface normal with a new u = 418 38. This orientational change does not explain the enhancement of the SFG-VS intensities when adding Na I, implying the number density of the methanol molecules with a net polar ordering in the surface region also changed with the Na I concentrations. These spectroscopic findings shed new light on the salt effects on the surfaces structures of the polar organic solutions. It was also shown that the accurate determination of the bulk refractive indices and Raman depolarization ratios for different salt concentrations is crucial to quantitatively interpret the SFG-VS data. 展开更多
关键词 Surface orientation Air/liquid interface Salt effect Sum frequency generation METHANOL
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